'Sons of God and the daughters of men' Who ?

Gen. 6: 1-4 is only an adaptation of an ancient legend. The cause that is attributed to the birth of mighty men of old before whom the Jews were like grasshoppers (Nu. 13: 33) is a mixed marriage which the Jews hated. Details cannot be pressed and none can be dogmatic as to who the sons of God and daughters of men were. The former could be either angels, or men in general or those who were the descendents of Seth and the latter women in general or daughters from the line of Cain (See Jerome Commentary or any, other good commentary). Mythological theme behind the J narrative is accepted and included in the Old Testament. The inspired author's contribution is the introduction of Jahweh in verse 3; The Jehovah said "My spirit shall not abide in man for ever, for he is flesh, but his days shall be a hundred and twenty years." Giants like Nephilim were born out of unholy alliance of the good with the evil and so the age of human being is reduced from 967 years of Methusaleh of the previous chapter to 120 years. The Deluge is also the punishment of such mixed marriages and the consequent wickedness of the off springs. The lesson for the modern student is that marriage partners should be carefully chosen from the sons of God and daughters of God and not from the wicked.